Harmful effects to the eye from ultraviolet (UV) light (from about 200 nm to about 400 nm in wavelength) have long been known. UV light reaching the eye has wavelengths in the range of UV-B and UV-A (i.e., from about 280 nm to about 400 nm) and has been linked to ocular disorders of the cornea, lens and retina including macular degeneration. Accordingly, most if not all, polymeric intraocular lenses include one or more UV absorbing compounds to block the transmission of the shorter wavelengths of light of the natural solar spectrum. More recently, a similar link to the same ocular disorders by visible violet light having wavelengths from about 400 nm to about 460 nm has also been discussed. UV light is said to account for about 67% of acute UV-blue phototoxicity between 350 nm and 700 nm, and violet light is said to be responsible for about 18% of acute UV-blue phototoxicity.
The natural lens is an essential component of the light filtering system of a human eye. From age twenty on, the crystalline lens absorbs most of the UV-A radiation (between about 315 and about 400 nanometers), protecting the retina from the damaging effect of this radiation. However, when a natural lens is surgically removed as a result of cataractogenesis, the retina is no longer protected from the damaging effect of UV-A radiation. One approach used to restore normal vision is achieved by surgical insertion of an artificial polymeric lens in the eye as a substitute for the removed lens. These artificial lenses are known as intraocular lenses (“IOLs”). Therefore, any IOL intended to act as a substitute for the natural lens should provide protection to the retina against UV radiation.
U.S. Pat. No. 4,304,895 discloses the use of 2-hydroxy-4-methacryloyloxy-benzophenone and mixtures thereof as a monomeric ultraviolet light absorber copolymerizable with acrylic monomers and useful in the preparation of UV absorbing hard contact lenses. Similarly, the copolymerization of an allyl-2-hydroxy-benzophenone with an acrylate ester such as methyl methacrylate is described in U.S. Pat. No. 4,310,650, and, the copolymerization of ethylenically unsaturated derivatives of 2,4-dihydroxy benzophenone with other vinyl type comonomers is broadly disclosed in U.S. Pat. No. 3,162,676. The reported polymers that incorporate the bis-hydroxy-benzophenone compounds have little or no absorption in the violet spectral range (about 410 nm to 440 nm) even at concentrations up to 3 wt. %. In these polymers one typically observes a sharp transmission profile centered at about 380 nm with less than 20% absorption at 400 nm.
U.S. Pat. No. 4,528,311 discloses certain benzotriazole monomers which are copolymerizable with vinyl monomers such as methyl methacrylate to yield optically clear polymers useful in the preparation of intraocular and contact lenses. Representative of the disclosed benzotriazole monomers and a particularly preferred compound is 2-(2′-hydroxy-5′-methacryloyloxypropyl-3′-tert-butylphenyl)-5-chloro-2H-benzotriazole. U.S. Pat. No. 4,716,234 discloses certain benzotriazole monomers that are also copolymerizable with vinyl monomers. The benzotriazole monomers are defined by the general formula
wherein R1 is H, halogen or alkoxy of 1 to 3 carbon atoms, R2 is H or an alkyl with 4 to 6 carbon atoms, and R3 is a C2-C10 alkylene with an ethylenic polymerizable group.
Though not a critical for eye protection, there has been recent efforts of making contact lenses available with UV protection. The contact lens should not be a complete substitute for a good pair of sunglasses on a very sunny day, but contact lenses with some UV protection may prove to be clinical beneficial in some patients. For at least these reasons, there is this recognized need to provide means for protecting the human eye, e.g., the retina, from the potential harmful effects of solar radiation. In this manner, it is very desirable to provide artificial lenses that absorb UV-A and/or UV-B radiation, and perhaps, at least a portion of violet light.